The effect of disorder on electronic Raman scattering in the superconducting state of iron pnictides

TL;DR

This paper investigates how disorder affects electronic Raman scattering in iron pnictide superconductors, using models and approximations to interpret experimental observations related to gap nodes and symmetry.

Contribution

It provides a theoretical analysis of disorder effects on Raman spectra in iron pnictides, including various gap symmetries and scattering regimes, to interpret experimental data.

Findings

Disorder can lift nodes in the superconducting gap.

Raman spectra are sensitive to the type and strength of disorder.

Experimental data on Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ may be explained by intraband disorder effects.

Abstract

Electronic Raman scattering measures a polarization-dependent scattering intensity which can provide information about the location of nodes in the energy gap of an unconventional superconductor as well as its overall symmetry. In this paper, we calculate the Raman intensity in the presence of disorder for several models of the iron pnictide superconducting state. We include, for completeness, $d$-wave and isotropic $s_\pm$ responses in addition to more realistic extended $s_\pm$ superconducting gaps. The effect of disorder is modeled using a self-consistent $T$-matrix approximation, and is studied in the limits of isotropic and intraband-only scattering. We show how recent experiments on Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ may be consistent with "node lifting" by intraband disorder.